In animal breeding, there is a general ambition to use technology for automation of various operations, such as foddering, milking, for the purpose of reducing the staff requirement and, consequently, keeping the costs down. At the same time, such technical equipment is required that the qualities in animal breeding can be maintained or improved. The technology used should also be possible to manufacture and service at costs that would make it applicable not only in large-scale breeding, but also in small and medium-size animal breeding plants.
A common requirement is that it should be possible to identify and/or determine the position of individual animals, collectives of animals, as well as defined parts of animals, e.g. to be able, when foddering, to portion the correct amount of fodder, correctly composed, or to be able to establish the position of the udder and teats of a cow at a milking station.
The problem in identifying cows in the first place has been solved by providing each individual with a so-called transponder which contains ID information on the cow and can be read as the cow passes defined interrogation stations. However, in a more general monitoring of stock of animals, there remains a wish to be able to determine the position as well as, where appropriate, identify both individual animals and collectives of animals without necessitating the provision of said transponders and the cows passing an interrogation station. For instance, this may involve the monitoring of animals moving freely in an enclosed pasture or cow-house.
In many applications, great accuracy is required at the same time as the sensing should be able to take place at a great or small distance. This has resulted in methods and systems that are based on image information from the animals, the animal or portions of the animal, which is recorded by one or more video cameras. These cameras can be of conventional type and the image information can be recorded in black and white, but preferably the recording takes place in colour to permit the most accurate evaluation. The video cameras can be of the type operating with an electronic tube, but are preferably of the CCD type, having, for instance, the advantage of a smaller weight and a construction which, generally seen, is more durable. By using standard-type video cameras, the costs can be kept down, at the same time as it is possible to work with a well-developed technology.
Regarding milking and foddering, there are several motives for automated milking. Thus, one wants to reduce the staff requirement in order to keep the costs down and at the same time eliminate the ergonomically unsuitable operations in connection with milking. An automated milking procedure also makes it possible to increase the number of milking occasions a day, and to perform milking independently of the time of the day, which has been found to result in a considerably increased milk production.
Milking stations of the type in question are intended for cattle moving freely and finding the milking station on their own. During milking, the cow is standing in a stall which is closed by an automatically operated gate or like means, which makes the cow take a reasonably well defined position in the stall. In order to eliminate the risk of injuries, one strives to provide a quiet milking situation, which makes the cow stay fairly calm. This requires in turn that the milking procedure is carried out quickly and with great accuracy. Even under favourable conditions, one cannot expect the cow to stay quite calm in the stall, since there is a certain space for movements. Moreover, the individuals behave in different manners. This results in the udder and teats of the cow moving, which as a rule causes problems in the automatic application of teat cups and/or the guiding of other equipment in the context.
Generally seen, there are two main techniques of applying the teat cups: on the one hand at the same time as a milking means, where the teat cups are located in a holder with adjustable teat cup positions by a robot arm being raised towards the udder and, on the other hand, by applying the teat cups one by one to the respective teat by means of a guidable robot arm which collects the teat cups from a rack. Preferably the latter method is used since it allows greater flexibility and accuracy.
Prior art presents many attempts at solving the problem in the automatic application of teat cups. For instance, use has been made of sensors, e.g. IR sensors which sense, at a distance, the position of udder and teats in the horizontal plane, supplemented with additional sensors of the same or a corresponding kind, arranged on or adjacent each teat cup for accurately adjusting its position when the teat cup is raised towards the udder/teat. The experiments with this type of arrangement and the like have, however, not been satisfactory so far.
The development in this field has also led up to the suggestion of using image information, preferably colour image information, from one or more video cameras and subsequent image analysis for controlling the application of teat cups. The information content in a colour image is very great and thus provides the conditions for achieving the desired accuracy. The great amount of information is, however, in conflict with the demand for high speed information processing and accompanying excellent dynamics and precision in the system. Rapid processing of large data sets requires a great computer capacity, which in turn causes problems in manufacturing a technical installation at costs that can be defrayed by the expected savings. The computer power costs also render it difficult to develop a milking station which is suited not only for large-scale production but also for medium-size and small stock of animals.
An example of prior-art technique using video cameras for recording image information is to be found in GB-A-2,272,971, which discloses the use of two video cameras for recording colour image information at a milking station for the purpose of ascertaining whether the udder and teats of the cow are dirty or injured. This publication contains no detailed description of the processing of the image information, but it is established that colour images can be used and processed in real time, provided that a sufficient data processing capacity is available.
DE-37 44 867 C2 also discloses the use of video cameras at a milking station for applying teat cups to the cow's udder. The locating of a teat is intended to take place by so-called contour comparison between a significant contour characteristic of a teat, such as the tip thereof, in a recorded image and a reference contour. Nothing is said in this patent specification about the manner in which this significant contour information should be extracted from a recorded video image and how this significant contour information is then compared with a reference contour. This type of image or contour comparison usually implies large sets of data, thus necessitating a great data processing capacity. The use of the method at a milking station also requires that the image processing be carried out in real time, which further increases the demands for available data processing capacity.
The use of colour image information to achieve the greatest possible information accuracy consequently is in direct conflict with the demand that the technical installation involved should be possible to manufacture at costs that are acceptable in the situations of use. It is possible to get an idea of the data quantities involved by establishing that an image frame of the video information consists of two image fields, and that the field frequency is e.g. 50 Hz. From a current type of video camera, there is obtained for each field a data quantity consisting of 768*290 pixels (the number of pixels per line * the number of lines per field), where each pixel in turn contains 24 bits of colour information. If it is required that the processing of this data quantity occur in real time, i.e. within the recording time of the field, the available space of time is 20 ms, which corresponds to a processing speed of about 267 Mbit/s. Processors that are available today do not cope with this processing speed, especially if they are processors in so-called built-in systems, which are also required to manage input/output, have a moderate consumption of power and involve purchase costs that are reasonable in the context.